Introduction
This chapter contains a selection of cases from struc- tures surrounding the maxillofacial area. It is not the intention to cover all abnormalities in these regions, but instead to give the maxillofacial radiologist a feel and sense for radiographic abnormalities that may occur in areas adjacent to the maxillofacial region.
Thus, we have selected characteristic and illustrative cases from the cervical spine, neck, skull base, and or- bit that are likely to be seen on maxillofacial imaging studies. The chapter includes chronic and acute con- ditions, tumors, inflammation, and degenerative changes, and is divided into four parts: cervical spine, neck, skull base and orbit. For a more complete re- view of imaging findings of these areas we refer the reader to traditional textbooks on head and neck im- aging.
Cervical Spine
A portion of the upper cervical spine will in many cases be depicted on regular maxillofacial imaging studies. This pertains to plain films of the jaw, lateral cephalograms, panoramic images, and MRI and CT scans of the maxillofacial region. This short review of cervical spine abnormalities has been done with this in mind. It is not the purpose to present a complete atlas of cervical pathology, but instead to illustrate those cases that the maxillofacial radiologist is likely to encounter. Thus, we have included mostly bony ab- normalities but some soft tissue lesions are also illus- trated. There are many more conditions affecting the cervical spine than we have illustrated such as de- myelinating disease, spondylosis, and nerve root compression to give a few examples.
Calcific Tendinitis Longus Colli
Definition
Recurrent deposits of crystalline calcium com- pounds within the longus colli muscle.
Clinical Features
▬
Diagnosis based upon clinical presentation and imaging.
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Cervical pain, dysphagia, and distinctive radi- ographic appearance.
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Symptoms usually manifest over a few days and often resolve benignly within 2 weeks.
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Often unrecognized cause of acute to subacute neck pain.
▬
Self-limiting disease which resolves spontaneous- ly with symptomatic treatment.
Imaging Features
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Calcification at C1-C2 level with prominence of prevertebral soft tissues.
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Pathognomonic lateral neck film with prevertebral soft-tissue swelling and amorphous radiodensity anterior to C1-C2 vertebral bodies.
▬
CT, axial scans, highly reliable for diagnosis.
Adjacent Structures;
Cervical Spine, Neck, Skull Base and Orbit
In collaboration with M. Oka · R. Sidhu · N. Kakimoto
Figure 13.1
Calcific tendinitis longus colli; 47-year-old male with neck pain, clinical question of retropharyngeal abscess or phlegmon in neck.A Lateral view shows calcific density anteriorly between C1 and C2 (arrow) with slightly prominent soft tissues.
B Axial CT image shows a prevertebral calcification (arrow). No mass or lymphadenopathy
A B
Ossification of Posterior Longitudinal Ligament
Definition
Calcification of posterior longitudinal ligament of spinal column.
Clinical Features
▬
Histologically this mostly represents ossification rather than amorphous calcification.
▬
Most commonly affects cervical spine.
▬
More common in Japan for unknown reasons.
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Often causes neurological symptoms secondary to narrow spinal canal.
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More frequent in males than females.
Imaging Features
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CT highly reliable for diagnosis.
▬
Often causes significant spinal canal stenosis.
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On axial CT images posterior longitudinal liga- ment is seen as a “mushroom”,“hill”,“square”, or a mixture of these shapes.
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Four morphologic forms: continuous and seg- mental forms account for 95%.
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Characteristic sharp radiolucent line separates os- sified posterior longitudinal ligament from poste- rior vertebral margin; about 50% of cases.
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Segmental form of ossified posterior longitudinal ligament needs to be differentiated from calcified discs and posterior osteophytes; neither of these two conditions shows a characteristic sharp radi- olucent line and in contrast to ossified posterior longitudinal ligament, osteophytic growth is along a horizontal axis.
▬
Differential diagnosis:
– Ankylosing spondylitis, which more commonly affects the lumbar spine with syndesmophytes rather than ossification of posterior longitudi- nal ligament.
– DISH (diffuse idiopathic skeletal hyperostosis) which is a more generalized condition with ex- tensive calcification and ossification, particular- ly in spine.
Figure 13.2
Ossification of longus colli ligament; 55-year-old male with a 5-year history of cervical and lumbar radiculopathy; no neu- rologic deficit on examination.A Axial CT-myelography of cervical spine shows ossified posterior longitudinal ligament having a mushroom-shaped appearance at C4-C5 level (arrow).B Well-appreciated lucent line between posterior margin of vertebral body and ossified ligament (arrow), representing connective tissue
A B
Figure 13.3
Ossification of longus colli ligament; 52-year-old female with a history of left arm pain and clinical suspicion of cervical disc displacement or mass.A Axial CT image shows mushroom-shaped ossification (arrow) with radiolucent line between ossification and vertebral body.B Sagittal CT image shows ossification between C2 and C3 (arrow), and segmental ossifi- cation at C4-C7, as well as anterior osteophytes C3-C4 consistent with degenerative changes (arrowhead).C Lateral view of another patient shows severe ossification (arrow).D Axial T1-weighted MRI, same patient as in C, shows evident ossifi- cation (arrow) anterior to longus colli muscles (arrowheads)
A
C D
B
Rheumatoid Pannus at Craniocervical Junction
Definition
Hypertrophied synovitis with production of inflam- matory joint fluid containing several different types of enzymes.
Clinical Features
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Cervical spine pain and limitation of motion.
▬
Enlargement of retrodental pannus can induce or aggravate compressive myelopathy.
Imaging Features
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MRI is superior imaging method; shows both in- flammatory soft tissue and compression of spinal cord.
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MRI depicts effect of inflammatory process on neural tissue, ligaments, bursae, and fat pads.
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Pannus; often low signal on T1-weighted and high signal on T2-weighted MRI, showing contrast en- hancement, depending on activity of inflammation.
▬
Atlantoaxial dislocation or cranial migration of dens may be seen.
Figure 13.4
Rheumatoid pannus at craniocervical junction; 46-year-old female with long history of rheumatoid arthritis, now with cervical spine pain.A Sagittal T1-weighted MRI shows hyperintense mass anterior to eroded dens (arrow).B Sagittal T2-weighted MRI shows same mass to be markedly hyperintense with a few heterogeneous foci (arrow). Kyphotic defor- mity of mid-cervical spine and degenerative changes at C5–C6 in particular
A B
Tuberculosis at Craniocervical Junction
Definition
Granulomatous or caseous type inflammation caused by Tuberculum bacilli.
Clinical Features
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Pain, rigidity, deformity, cold abscess and paraple- gia.
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Thoracolumbar commonest site.
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Can occur as paradiscal, central body, subligamen- tous type, and appendiceal.
▬
Commonly involves two or three vertebrae.
Imaging Features
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Progressive bone destruction leads to collapse.
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Often paraspinal phlegmon.
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T1-weighted MRI: low signal.
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T2-weighted MRI: high signal, depending on ac- tivity of inflammation.
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T1-weighted post-Gd MRI: enhancing of inflam- matory granulomatous tissue.
Figure 13.5
Tuberculosis at craniocervical junction; 50-year-old female presented with history of neck ache and low-grade fever for two months.A Axial T1-weighted post-Gd MRI shows destruction and erosion of atlantoaxial joint with an enhancing soft-tissue mass (arrows). A small epidural component is seen causing pressure on thecal sac (arrowhead).B Sagittal T1-weighted MRI shows destruction of C1 and C2 with a soft-tissue mass (arrow) (courtesy of Dr.Humera Ahsan,Aga Khan University, Karachi, Pakistan)
A B
Chiari Malformation Type I
Definition
Herniation of cerebellar tonsils through foramen magnum into cervical spinal canal.
Clinical Features
▬
Often nonspecific symptoms such as headache,neck pain, dizziness, vertigo, or cranial nerve symptoms.
▬
Chiari I is often an incidental finding and has no clinical implication in absence of symptoms.
Imaging Features
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Cerebellar tonsil located more than 5 mm inferior to a line between hard palate and posterior lip of foramen magnum.
▬
More common in children.
▬
Chiari I is often difficult to see, but a “full” foramen magnum on axial CT images is a good sign.
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There are no osseous abnormalities.
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MRI shows peg-like tonsils below foramen magnum.
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Narrow posterior cranial fossa.
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Associated syringomyelia or syrinx (CSF in center of spinal cord) may be seen.
▬
Restricted CSF flow due to cerebellar tonsil being displaced inferiorly into foramen magnum.
Figure 13.6
Chiari malformation type I; 7-year-old female with Noonan syndrome presents with neck pain. Mid-sagit- tal T1-weighted MRI shows descent of point of tonsils through foramen magnum (arrow) and absence of CSF in cisterna magna
Figure 13.7
Chiari malformation Type I; 5-year-old asymptomatic male.A Mid-sagittal T1-weighted MRI demonstrates caudal dis- placement of cerebellar tonsils (arrow). Dark signal in center of cervical cord represents syringo- or hydromyelia with mul- tiple locations (arrowheads).B Sagittal T2-weighted MRI reveals associated hydromyelia with multiple locations of fluid in center of cord. These are sequelae of decreased CSF dynamics through foramen magnum (arrows)
A B
Chordoma at Craniocervical Junction
Definition
Benign but locally aggressive and infiltrating tumor arising from notochordal remnants along neuraxis.
Clinical Features
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Presents with pain and/or neurologic symptoms.
▬
Commonest location sacrum, followed by clivus, and spinal axis.
▬
Slow-growing tumor with destruction of adjacent bone.
Imaging Features
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Destructive expansile lesion in spine with sur- rounding soft-tissue mass.
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Locally aggressive.
▬
Destruction and calcification better seen on CT images.
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T1-weighted MRI: iso- to hypointense.
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T2-weighted MRI: moderately to extremely hyper- intense; extreme T2 hyperintensity is often a hall- mark of chordoma, but not seen in our case (Fig. 13.8B).
▬
T1-weighted post-Gd MRI; variable enhancement.
A B
Figure 13.8
Chordoma at craniocervical junction; 3-year-old female with a history of anorexia and lethargy for two months, presenting with mild cervical spine pain.A Sagittal reconstructed CT image shows destruction and bone production in skull base (arrow) and C1 area.Top of dens is eroded (arrowhead). B Sagittal T2-weighted MRI shows a large hypointense expansile mass emanating from the clivus (arrow).C Sagittal T1-weighted post-Gd MRI demonstrates a slight enhancement of mass (arrow) involving the clivus, C1 and C2, and extending intracranially and into foramen magnum and nasophar- ynx.D Axial CT image through foramen magnum illus- trates destruction anteriorly (arrow) and bone produc- tion.E Axial T1-weighted post-Gd MRI demonstrates irregular slightly enhancing destructive mass in fora- men magnum (arrow) extending into the brain stem, causing brain stem compression
C D
E
Cervical Spine Teratoma
Definition
True neoplasm consisting of all three embryonic lay- ers.
Clinical Features
▬
The most common tumors outside of the spinal cord (extra medullary) in cervical spine of new- borns are neurofibromas/schwannomas followed by drop metastases and congenital lesions.
▬
Teratoma is a rare tumor.
▬
Approximately 10% associated with other congen- ital anomalies.
Imaging Features
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Often large relatively well circumscribed lesions.
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Usually well-encapsulated, with both cystic and solid components.
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Fat content is typical.
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T1- and T2-weighted MRI: heterogeneous signal due to difference of cellular components.
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T1-weighted post-Gd MRI: contrast enhancement of solid portions.
Figure 13.9
Spinal teratoma; 7-year-old female with right hemipare- sis.ASagittal T2-weighted MRI shows enlargement of upper cervical canal. Anterior to cord there is hypo- intense mass displacing cord (arrow). Exophytic mass largely fills spinal canal with almost complete oblitera- tion of CSF space. Only posterior margin appears to infiltrate cord. Syrinx is seen below mass (arrowhead).
BSagittal T1-weighted post-Gd MRI shows near homo- geneous enhancement (arrow), but no cord enhance- ment. C Axial T2-weighted MRI shows mass (arrow) compressing and displacing cord posteriorly
A
C
B
Cervical Spine Cord Astrocytoma
Definition
Tumors derived from the glial cells (astrocytes or
“star-shaped” cells).
Clinical Features
▬
Most common intramedullary (inside spinal cord) spinal cord tumor in children.
▬
Cervical spine commonest site of involvement.
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Multisegmental involvement usually seen.
▬
Cysts and syrinx formation common.
Imaging Features
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Expansion of cord.
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Cord edema.
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Cysts are common.
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Relatively short segment involved as opposed to transverse myelitis in which a longer segment of cord is affected.
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T1-weighted MRI: iso- to slightly hypointense.
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T2-weighted MRI: hyperintense.
▬
T1-weighted post-Gd MRI: patchy contrast en- hancement.
Figure 13.10
Spinal cord astrocytoma; 8-year-old female with known low-grade astrocytoma in cervical cord since age of 18 months when she presented with breathing and swallowing difficulties. Sagittal T1-weighted post-Gd MRI shows intense contrast enhancement in tumor (arrow), extending into medulla and lower pons (arrow- head)
Extramedullary Cervical Lipoma with Cord Compression
Definition
Benign fatty tumor, usually composed of mature fat cells.
Clinical Features
▬
Initially asymptomatic mass.
▬
Presents with symptoms of spinal cord compres- sion.
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Often congenital.
▬
Most common connective tissue tumor of spine.
Imaging Features
▬
CT: homogeneous non-enhancing mass with fatty attenuation value.
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T1- and T2-weighted MRI: hyperintense.
▬
T1-weighted fat-suppressed MRI: hypointense.
Figure 13.11
Extramedullary cervical lipoma with cord compression;
patient had long history of cord compression symp- toms. Surgery confirmed the location and fatty nature of the encapsulated tumor.A Sagittal proton density MRI shows a large intradural mass (arrow), secondarily widened canal to longstanding pressure tumor.B Sagit- tal T2-weighted MRI shows slightly hyperintense mass compared to spinal cord. Note chemical shift misregis- tration artifact at CSF/lipoma and lipoma/CSF borders (arrowheads). C Sagittal T1-weighted fat-suppressed MRI shows fatty nature of tumor (arrow)
A
C
B
Cervical Spine Meningioma
Definition
Tumor arising in meninges surrounding brain and spinal cord.
Clinical Features
▬
Peak incidence in fifth to sixth decade with female predominance.
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Thoracic spine commonest followed by cervical spine.
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Majority are intradural extramedullary.
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Patients with neurofibromatosis type 2 (NF-2) can have multiple meningiomas, with intracranial occurrence and along spinal axis; meningiomas originate from meningothelial cells which may be found in spinal arachnoid membranes.
Imaging Features
▬
Similar characteristics to schwannoma.
▬
Calcification not uncommon.
▬
T1-weighted MRI: isointense to cord.
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T2-weighted MRI: hypointense to cord.
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T1-weighted post-Gd MRI: homogeneous and sig- nificant contrast enhancement.
Figure 13.12
Meningioma; 67-year-old woman with progressive weakness in both lower extremities and pain in both arms. Remote history of breast cancer.A Sagittal T2-weighted MRI shows well-defined mass with homogeneous signal isointense to cord (arrow).B Sagittal T1-weighted post-Gd MRI shows intense contrast-enhanced tumor (arrow)
A B
Cervical Spine Neurofibromatosis Type 1 (NF-1)
Definition
Tumors arising from nerve sheath of peripheral nerve; Schwann’s cells, fibroblasts, and perineural cells.
Clinical Features
▬
NF-1 the commonest neurocutaneous syndrome.
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Manifestations can arise from any system of body.
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Bony changes usually associated.
▬
Many patients have neurofibromas in cervical re- gion.
Imaging Features
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Iso- to hypodense to muscle on CT
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Spinal lesions best seen on MRI
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T1-weighted MRI: neurofibromas appear iso- to hypointense.
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T2-weighted MRI: hyperintense
▬
T1-weighted post-Gd MRI: strong contrast en- hancement; may show “target pattern”
Figure 13.13
Neurofibromatosis type 1 (NF-1); 16-year-old female with known NF-1, presenting with balance and coordi- nation problems. Sagittal T2-weighted fat-suppressed MRI shows enlargement of the neural foramina with multiple rounded neurofibromas (asteriscs)
Cervical Spine Fracture
Definition
Fracture and/or dislocation of cervical spine.
Clinical Features
▬
Presents invariably with cervical spine pain or ten- derness.
▬
More advanced fractures neurologic symptoms.
▬
Plain films often negative.
Imaging Features
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CT, sagittal and coronal images, best for fracture diagnosis.
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MRI best for cord injury and for ligamentous in- juries.
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Burst fracture involves fracture of posterior wall of vertebral body often with retropulsion.
▬
Compression fracture has intact posterior wall of vertebral body.
Figure 13.14
C5 burst fracture; 27-year-old male all-terrain vehicle accident.ASagittally reformatted CT image shows burst fracture of C5 with subluxation and severe central canal narrowing (arrow).BAxial CT image demonstrates frag- ment displaced into central canal (arrow). Also fracture through right foramen tranversarium where vertebral artery is located.This injury may cause damage to verte- bral artery which could lead to a posterior fossa stroke.
C Sagittal STIR MRI shows spinal cord contusion, C5 burst fracture (arrow), prevertebral hematoma C1 to C4 (arrowheads) and injury to posterior elements (large ar- rowhead)
A
C B
Neck
Diagnosis of lesions of the suprahyoid neck is prima- rily not the duty of the maxillofacial radiologist.
However, many of the structures of this area will be depicted on regular maxillofacial imaging studies and therefore the maxillofacial radiologist will often have to make a gross evaluation to determine whether there is an abnormality that needs further attention or the structures are normal. Conversely some larger maxillofacial lesions will extend into the suprahyoid neck and the maxillofacial radiologist will have to have a working knowledge of neck anato- my in order to formulate an interpretation of the findings.
This section is included to provide examples of ab- normalities in the supra- and infrahyoid neck that may be recognized by the maxillofacial radiologist, such as inflammations, nontumorous expansive masses, muscle paralysis, and benign and malignant tumors with their characteristics.
Hypopharynx Abscess
Definition
Pus collection in pharyngeal/hypopharyngeal soft tissues.
Clinical Features
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Dysphagia
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Neck and oral pain
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Fever
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Stridor
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Odynophagia
Imaging Features
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Soft-tissue swelling
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Ring-enhancing lesion with low attenuation center
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Stranding (lymphedema) and obliteration of adja- cent fat planes
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Thickening of platysma
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Lymphadenopathy
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T1-weigted MRI: decreased signal
▬
T2-weighted MRI: increased signal
▬
T1-weighted post-Gd MRI: peripheral enhance- ment
Figure 13.15
Hypopharynx abscess; 48-year-old male presenting with a peripharyngeal soft-tissue swelling, neck pain, fever and stridor. Axial CT image shows multilobulated ring-enhancing mass (arrow), consistent with abscess in left hypopharynx with a compression narrowing and deviation of hypopharyngeal airway. Thickening of platysma (arrowhead) and stranding of subcutaneous fat
Thyroid Abscess
Definition
Well-circumscribed pus collection within thyroid gland.
Clinical Features
▬
Swelling, pain, redness.
▬
Induration (localized hardening of soft tissue).
▬
Fever.
▬
Dysphagia/odynophagia.
▬
Tender gland sometimes with referred pain to pharynx/ear.
▬
Often occurs in immunocompromised and debili- tated patients.
▬
Staphylococcus aureus, Pneumococcus common organisms.
Imaging Features
▬
Ring-enhancing lesion with central area of necro- sis within thyroid gland
▬
Swelling
▬
Fat stranding
▬
Lymphadenopathy
Figure 13.16
Thyroid abscess; 19-year-old female presenting with a 2-week history of a sore throat, left neck pain, and headache. Axial post-contrast CT image shows ill- defined hypodense lesion in left lobe of the thyroid gland with ring enhancement (arrow), consistent with abscess and soft-tissue edema. Low dense areas are also noted in oropharynx especially on the left side and inferiorly to the thoracic inlet, and bilateral lymph- adenopathy
Tornwaldt’s Cyst
Definition
Developmental cyst occurs when pharyngeal bursa ectoderm retracts with the notochord into the clivus.
Named after Gustav Ludwig Tornwaldt (1843–1910).
Clinical Features
▬
Most often asymptomatic incidental finding on imaging study.
▬
Seen incidentally in up to 3% of healthy adults;
usually no treatment need.
▬
May cause symptoms when infected.
▬
Infection may spread to mediastinum.
Imaging Features
▬
Cystic lesion mostly in mid-line of nasopharynx
▬
Low attenuation
▬
T1-weighted MRI: low signal intensity
▬
T2-weighted MRI: high signal
▬
T1-weighted post-Gd MRI: no contrast enhance- ment
Figure 13.17
Tornwaldt’s cyst, large; incidental findings in 30-year-old.A Sagittal T1-weighted MRI shows low-signal cyst (arrow) in posterior nasopharynx.B Axial T2-weighted MRI shows bright signal cyst (arrow).C Coronal T2-weighted MRI shows bright signal cyst (arrow).D Coronal T1-weighted post-Gd MRI shows no enhancement of the cyst (arrow)
A B
D C
Dermoid Cyst in Floor of Mouth
Definition
Growth of a piece of skin underneath the surface as result of abnormal development; may contain skin, hair, bone, teeth or embryonal tissue.
Clinical Features
▬
Most commonly involves floor of mouth; sublin- gual, submental, or submandibular regions.
▬
Differential diagnosis includes epidermoid, ranu- la, thyroglossal duct cyst, and cystic hygroma.
▬
Soft nonpainful mass.
Imaging Features
▬
Typically well-circumscribed, thin-walled, unil- ocular mass
▬
Low attenuation
▬
T1-weighted MRI: homogeneous low signal
▬
T2-weighted MRI: homogeneous high signal
▬
T1-weighted post-Gd MRI: no contrast enhance- ment of cyst except wall, in particular if infected
Goiter
Definition
Diffuse or multinodular enlargement of thyroid gland.
Clinical Features
▬
More common in middle-aged females.
▬
Often associated with iodine deficiency.
▬
Midline neck mass.
▬
Often asymptomatic enlargement of thyroid gland;
symptoms depend upon state of hypo- or hyper- thyroidism.
▬
Endemic goiters are prevalent in iodine deficient areas.
▬
Goiter is a clinical diagnosis that simply implies an enlargement of thyroid gland developing because thyroid gland compensates for inadequate thyroid hormone output.
Imaging Features
▬
Nodular enlargement of thyroid gland often with cystic lesions.
▬
Displaces and narrows trachea.
▬
Multinodular goiter is usually not associated with tumors.
▬
Substernal or mediastinal extension requires im- aging for detection.
▬
T2-weighted MRI: high signal due to colloid or hemorrhage.
▬
Nuclear scan with radioactive iodine or Tc-99m pertechnetate is often very helpful (cannot be done for 6 weeks if intravenous contrast has been used).
▬
Ultrasound is often used to characterize multi- nodular goiter.
Figure 13.18
Dermoid cyst; 18-year-old male with doughy swelling of floor of mouth clinically considered a thyroglossal duct cyst. Axial T2-weigted fat-suppressed MRI shows well-defined oval mass with high signal in floor of mouth (arrow), located in sublingual space depressing mylohyoid muscle down (not shown)
Figure 13.19
Goiter; 18-year-old presenting with hyperthyroidism.
Axial T2-weighted fat-suppressed MRI shows large mul- tilobulated thyroid gland compressing and narrowing trachea (arrow)
Vocal Cord Paralysis
Definition
Vocal cord does not move to center due to muscle paralysis.
Clinical Features
▬
Patient presents with hoarseness
▬
Occasionally a sign of a tumor along the recurrent laryngeal nerve
Imaging Features
▬
Paralyzed vocal cord is located laterally in larynx;
unable to migrate to midline (as normal) due to lack of innervation of muscles.
Neck Hemangioma
Definition
Hemangioma or benign neoplasm that exhibits in- creased blood circulation, endothelial cells, mast cells, and macrophages.
Clinical Features
▬
Most common tumor in head and neck in infancy and childhood.
▬
Approximately 7% of all benign soft-tissue tu- mors.
▬
Rapidly enlarges.
▬
Ultimately regresses by adolescence.
▬
Typically becomes apparent during the first month of life.
▬
Diffuse skin lesion or soft cystic mass in oral cavi- ty, pharynx, parotid gland, or neck.
▬
Associated with intracranial arterial vascular mal- formations.
▬
Often requires no treatment. Steroids are occa- sionally used.
Imaging Features
▬
T1-weighted MRI: intermediate signal with flow void
▬
T1-weighted post-Gd MRI: dramatic enhance- ment
▬
Often extensively infiltrative in nature
Figure 13.20
Right vocal cord paralysis secondary to lung cancer;
63-year-old man presents with hoarseness. Axial CT image through larynx shows right vocal cord (arrow) laterally in larynx
Figure 13.21
Hemangioma; 6-month-old infant twin girl presents with mass in back of neck. The mass has been observed for only a few days.A Sagittal T1-weighted MRI shows a well-circumscribed large mass in posterior neck with flow voids (arrow).B Sagittal STIR MRI shows intermedi- ate high signal intensity also with flow voids (arrow).
C Sagittal T1-weighted post-Gd MRI shows dramatic enhancement (arrow).
A
C B
Neck Lipoma
Definition
Benign fatty neoplasm.
Clinical Features
▬
Often occurs in posterior neck.
▬
Soft benign neoplasm, usually does not enlarge in size.
Imaging Features
▬
Low attenuation
▬
Well-circumscribed
▬
T1-weighted MRI: high signal
▬
T2-weighted MRI: intermediate signal
▬
T1-weighted fat-suppressed MRI: low signal
Figure 13.22
Lipoma; 8-year-old female with a 3-week history of left posterior neck mass. No redness, no fever and no ten- derness. Axial CT image shows low-attenuation well- circumscribed fatty appearing mass in posterior trian- gle of left neck (arrow), deep to sternocleidomastoid muscle
Neck Plexiform Neurofibroma
Definition
Benign neoplasm consisting of Schwann cells and fibroblasts.
Clinical Features
▬
Malignant transformation in 5% to 10%.
▬
Unique to neurofibromatosis type 1 (from von Recklinghausen’s disease).
▬
Common in the scalp, neck, mediastinum, retro- peritoneum, cranial nerve five, and orbits.
▬
Masses are soft and elastic.
▬
Accounts for elephantiasis, seen in neurofibro- matosis.
▬
Sarcomatous transformation in about 5% of pa- tients.
Imaging Features
▬
Infiltrated aggressive appearing tumors along cra- nial nerves
▬
Multilobulated masses along nerves with low to intermediate attenuation.
▬
T1-weighted MRI: intermediate signal.
▬
T2-weighted MRI: high signal. Sometimes target sign: low signal intensity centrally with ring of high signal in periphery
▬
T1-weighted post-Gd MRI: often dramatic en- hancement
▬
Three types: localized, diffused, plexiform.
Figure 13.23
Plexiform neurofibromatosis; 9-year-old female pres- ents with a painless swelling of right lower neck.A Axial T2-weighted fat-suppressed MRI shows multilobulated complex mass in right lower neck extending across midline (arrow), and separating common carotid artery and jugular vein, and abutting spine.B Axial T1-weight- ed post-Gd MRI shows enhancing mass separating carotid artery and jugular vein (arrow).CCoronal T1- weighted post-Gd MRI shows contrast-enhanced multi- lobulated mass in carotid sheath (arrow).
A
C B
Pharynx Rhabdomyosarcoma
Definition
Malignant tumor of striated muscles, primarily af- fecting children and young adults.
Clinical Features
▬
Most common malignant orbital tumor in childhood
▬
Mean age 7 years
▬
Often metastasizes to lung or cervical nodes
Imaging Features
▬
Large, aggressive soft-tissue mass.
▬
Ill-defined inhomogeneous large soft-tissue mass which erodes and infiltrates surrounding struc- tures including bones.
▬
MRI is best to characterize the soft tissue and extent.
▬
T1-weighted MRI: intermediate signal.
▬
T2-weighted MRI: hyperintense.
▬
T1-weighted post-Gd MRI: variable enhancement
Figure 13.24
Rhabdomyosarcoma; 5-week-old female with stridor and a posterior pharyngeal mass.A Axial T1-weighted MRI shows a large right pharyngeal mass isointense to muscle (arrow).B Axial T2-weighted MRI shows a well-circumscribed mass (arrow) in nasopharynx with linear and punctate areas of low attenuation representing vascular structure.C Contrast- enhanced T1-weighted MRI shows enhancement and flow voids (arrow).D Contrast-enhanced T1-weighted fat-sup- pressed MRI shows large enhancing lesion in nasopharynx (arrow)
A B
D C
Tongue Base Carcinoma
Definition
Squamous cell malignant neoplasm of the tongue.
Clinical Features
▬
Infiltrating lesion often on lateral or posterior aspect of tongue.
▬
Painless swelling and/or induration.
▬
Risk factors for oral cavity squamous carcinoma:
smoking, alcohol abuse, chewing tobacco, chewing betel nuts.
Imaging Features
▬
T2-weighted fat-suppressed image often delin- eates tumor best.
▬
Sagittal, coronal axial images are essential to as precisely as possible outline the extent of the tumor.
▬
Crossing the midline is important for surgical planning (generally not resectable if cross mid- line).
▬
T1-weighted MRI: intermediate signal.
▬
T2-weighted MRI: intermediate to high signal.
▬
T1-weighted post-Gd MRI: some enhancement.
Figure 13.25
Tongue base carcinoma; 64-year-old man presents with left throat pain.A Axial T2-weighted MRI shows a large low inten- sity mass in left tongue base extending to hypopharynx (arrow). The signal is higher than muscle but still not bright.
B Axial T1-weighted fat-suppressed post-Gd MRI shows slight enhancement of mass (arrow).C Axial T2-weighted MRI, more caudal section, shows no lymphadenopathy.D Axial T1-weighted fat-suppressed post-Gd MRI, more caudal section, shows extension to left hypopharynx (arrow)
A B
D C
Hypopharynx Carcinoma
Definition
Squamous cell malignant neoplasm of pharynx.
Clinical Features
▬
Infiltrating lesion in wall of pharynx
▬
Painless
▬
Often associated with swallowing problems
▬
Risk factors for hypopharynx squamous carcino- ma: smoking, alcohol abuse
Imaging Features
▬
Soft-tissue mass in hypopharynx
▬
Asymmetry of hypopharynx, supraglottic area, false and true vocal cords
▬
Obliteration of piriform sinus
Figure 13.26
Hypopharynx carcinoma; 60-year-old female with a feeling of a lump in the throat.A Axial T1-weighted post-Gd fat-sup- pressed MRI shows a large almost circumferential hypopharyngeal mass (arrow).B Axial T1-weighted MRI shows bila–
teral enlarged lymph nodes (arrows).C Coronal T1-weighted post-Gd MRI shows left-sided enlarged lymph node (arrows).D Coronal T2-weighted post-Gd MRI shows left-sided enlarged lymph node (arrows)
A B
D C
Burkitt’s Lymphoma
Definition
Stem cell non-Hodgkin’s lymphoma.
Clinical Features
▬
Most commonly seen in children
▬
Most common malignant disease of children in tropical Africa
▬
Involvement of jaw characteristic
▬
Related to Epstein-Barr virus
Imaging Features
▬
Rapidly growing soft-tissue mass
▬
Destruction of bone
Figure 13.27
Burkitt’s lymphoma; 7-year-old female with a 2-week history of large nontender neck mass. Axial post-contrast CT images (Bmore caudal than A) show a large soft-tissue mass (arrows) severely compressing internal jugular vein (arrowheads) and pushing midline structures towards other side. This appearance is nonspecific and the enlarged lymph node could be from any type of lymphoma or metastasis
A B
Castleman’s Disease
Definition
Benign lymph-node disease; angiofollicular hyper- plasia.
Clinical Features
▬
70% of cases present in chest, 10% in head and neck
▬
Often asymptomatic
Imaging Features
▬
Often intense enhancement due to hypervascular stroma.
▬
No central necrosis as seen in malignant lymph nodes.
▬
Differential diagnoses are mononucleosis, cat scratch disease and lymphoma.
Lymphadenopathy
Definition
Benign or malignant enlargement of lymph nodes.
Clinical Features
▬
Palpable nodal masses in neck.
▬
Often bilateral.
▬
Often painless unless infected.
▬
May be idiopathic or due to infection; other differ- ential diagnoses: lymphoma, mononucleosis, cat scratch disease, Castleman’s disease, HIV.
▬
Proportionally enlarged lymph nodes are often normally seen in young children.
Imaging Features
▬
Enlarged lymph nodes.
▬
No central necrosis if benign, but occasionally seen in malignant lymph nodes.
▬
Cannot separate specific etiology on imaging studies.
Figure 13.28
Castleman’s disease in 19-year-old male with relapsing/
remitting symptoms. Axial post-contrast CT image shows multiple slightly enlarged lymph nodes bilater- ally (arrows). From an imaging point of view these are nonspecific, and Castleman’s disease is not an imaging diagnosis
Figure 13.29
Lymphadenopathy; 40-year-old HIV-positive male.
Axial CT image shows enlarged lymph nodes bilaterally (arrows)
Figure 13.30
Lymphadenopathy; 42-year-old female with a history of nasopharyngeal carcinoma.A Axial T1-weighted MRI shows bilateral enlarged upper cervical lymph nodes (arrows).B Axial T1-weighted post-Gd MRI with fat sup- pression shows enhancement of enlarged lymph nodes (arrows).C Coronal T1-weighted post-Gd MRI with fat suppression shows many enhancing enlarged lymph nodes bilaterally (arrows)
A
C B
Skull Base
The skull base is the superior and posterior neighbor to the maxillofacial region. It involves the base of the skull with its foramina, muscles, nerves, and vascular structures. As in the other sections of this chapter, it is not the intention to give a full and complete description of skull-base abnormalities, but rather to illustrate conditions that are likely to be depicted on the images that the maxillofacial radiologist is asked to interpret, but still not in the true maxillofacial area. We have included characteristic infections, tumor-like and vascular lesions, and neoplasms.
Mastoiditis with Intracranial Abscess
Definition
Intracranial encapsulated pus collection due to pyo- genic infection secondary to mastoiditis.
Clinical Features
▬
Intracranial complications result from uncon- trolled coalescent mastoiditis.
▬
Intracranial complications of acute mastoiditis:
sigmoid sinus thrombosis, meningitis and abscess (subdural, epidural and parenchymal).
▬
Subperiosteal abscess can be seen.
▬
Common signs of mastoiditis: otalgia, postauricu- lar swelling and fever.
▬
Intracranial abscess may present with headache, seizure, fever, altered mental status, or focal neuro- logic deficits.
Imaging Features
▬
Non-contrast CT imaging: middle ear and mastoid completely opacified and mastoid air cells become confluent.
▬
Post-contrast CT imaging is first-line modality and shows rim-enhancing hypodense fluid collection.
▬
T1-weighted post-Gd MRI is best to diagnose sinus thrombosis and intracranial complications (venous infarct, meningitis and abscess).
▬
On diffusion-weighted MR imaging, abscesses are
bright indicating restricted diffusion.
Figure 13.31
Mastoiditis with intracranial abscess; 94-year-old female presented with a 1-week history of fever and mental status change. Patient treated with antibiotics for two episodes of right otitis media.A Post-contrast axial CT image demon- strates right mastoiditis with erosion of right petrous temporal bone (arrow), involvement of adjacent dura, and ring- enhancing lesion in right cerebellar hemisphere indicating abscess (arrowhead).B Sagittal T1-weighted post-Gd MRI shows hypointense lesion in right cerebellar hemisphere with ring enhancement (arrow).C Axial T2-weighted image demonstrates high intensity signal in right mastoid sinus and right cerebellar hemisphere with surrounding edema (arrowheads) and mass effect on fourth ventricle (arrow).D Diffusion-weighted imaging shows an area of hyperintensity in right mastoid sinus (arrow) and cerebellar hemisphere (arrowhead)
A B
D C
Mastoiditis with Sigmoid Thrombosis
Definition
Clot formation in sigmoid sinuses as a result of mas- toiditis.
Clinical Features
▬
Mastoiditis is a known cause of lateral venous sinus thrombosis.
▬
Sinus thrombosis may occur via direct extension or be the result of erosive osteitis and retrograde thrombophlebitis.
▬
Symptoms due to sinus thrombosis are variable:
asymptomatic to coma or death.
▬
May present with headache, nausea/vomiting or seizure.
▬
Hemorrhagic venous infarct may develop second- ary to poor venous drainage.
Imaging Features
▬
Non-contrast CT images: middle ear and mastoid completely opacified and mastoid air cells become confluent. May show hyperdense sigmoid sinuses.
▬
Post-contrast CT images: filling defect in sigmoid sinus, useful to diagnose intra- or extracranial abscess.
▬
Contrast MRI and MR venography are best to di- agnose sinus thrombosis and intracranial compli- cations (venous infarct, meningitis and abscess).
▬
On diffusion-weighted imaging, abscesses show hyperintensity with restricted diffusion.
Figure 13.32
Mastoiditis with sigmoid thrombosis; 7-year-old female with a chronic right draining ear.A Axial T1-weighted MRI shows soft-tissue mass in right temporal bone (arrow). There is no flow void in sigmoid sinus on this side.B Axial T1-weighted fat-suppressed post-Gd MRI demonstrates abnormal contrast enhancement in area of right temporal bone (arrows). In sigmoid sinus there is contrast enhancement in periphery but a central filling defect suggesting a clot (arrowhead).C Coronal MR venogram demonstrates lack of flow in right sig- moid sinus
A
C
B
Osteoradionecrosis Involving Skull Base
Definition
Nonvital bone in a site of radiation injury.
Clinical Features
▬
Serious complication of radiation therapy for neoplasms of the parotid gland, oral cavity, oro- pharynx, and nasopharynx.
▬
Predominantly in mandible.
▬
The risk is greatest during the first 6 to 12 months after radiation therapy, but osteoradionecrosis may develop several years later.
▬
Clinical diagnosis of mandibular osteoradio- necrosis is primarily based on clinical symptoms
and signs of ulceration or necrosis of the overlying mucous membrane with exposure of necrotic bone.
▬
Pathologic fracture and orocutaneous fistula may be seen.
Imaging Features
▬
CT image with bone window shows cortical dis- ruption and fragmentation.
▬
T1-weighted MRI: decreased marrow signal.
▬
T2-weighted MRI: increased marrow signal.
▬
Can be associated with significant soft-tissue thickening and enhancement in adjacent mastica- tor muscles
Figure 13.33
Osteoradionecrosis; 42-year-old male status postradiation treatment for nasopharyngeal cancer.A Axial CT image shows lytic and osteosclerotic changes of skull base bone (arrow).B Axial T1-weighted MRI shows hypointense lesion (arrow).
C Axial T2-weightd fat-suppressed MRI shows hyperintensity (arrow).D Axial T1-weighted fat-suppressed post-Gd MRI shows diffuse enhancement within clivus (arrow) and right masticator and buccal space (arrowheads)
A B
D C
Langerhans Cell Histiocytosis
Definition
A spectrum of disorders with histiocytic prolifera- tion involving bone and soft tissue.
Clinical Features
▬
Classified according to sites of involvement into single or multisystem disease.
▬
Usually presents in first decade.
▬
Bony involvement is seen in 78% of cases and of- ten includes skull (49%), innominate bone, femur, orbit (11%), and ribs.
▬
Infiltration in temporal bone presents with con- ductive hearing loss and draining ear.
▬
Frequently diagnosed only after treatment with antibiotics fails to cure a suspected middle ear or mastoid infection.
Imaging Features
▬
External auditory canal and mastoid are common locations.
▬
Bone margins are geographic and moderately well defined.“Punched-out” borders also may be found.
▬
Early imaging findings mimic inflammatory dis- ease.
▬
Post-contrast CT or MRI help to differentiate in- flammatory mastoid lesions.
▬
On CT images or MRI, enhancement within lesion may be homogeneous or may occur only in pe- riphery.
Figure 13.34
Langerhans cell histiocytosis; 1-year-old male who has had two episodes of otitis media and a recent onset of right auricular swelling.A Axial CT image shows soft-tissue mass with opacification and destruction of right mastoid air cells (arrow).B Coronal CT image with bone window shows irregular “geographic” border with complete loss of portions of mastoid cortex (arrow)
A B
Fibrous Dysplasia
Definition
Progressive replacement of normal cancellous bone by poorly organized fibro-osseous tissue.
Clinical Features
▬
Usually seen in young age group (<30 years old).
▬
Symptoms depended on the lesion location.
▬
Monostotic: 70% of cases, single osseous site is affected.
▬
Polyostotic: 25% of cases, involves more than two separated sites.
▬
Usually self-limiting, often does not progress after third decade of life.
▬
McCune-Albright syndrome: a variant that con- sists of polyostotic fibrous dysplasia, skin pigmen- tation and sexual precocity.
Imaging Features
▬
Affects any bone including skull, skull base and facial bones.
▬
Bone CT imaging is best for diagnosis showing expansile lesion centered in medullary space with variable attenuation.
▬
Ground-glass matrix in expansile bone lesion is typical.
▬
Abrupt or gradual transition zone between lesion and normal bone.
▬
T1- and T2-weighted MRI: low signal.
▬
T1-weighted post-Gd MRI: variable enhancement of internal matrix
Figure 13.35
Fibrous dysplasia; 4-year-old female with facial deformity.A Axial CT image with bone window shows ground-glass appearance of left maxillary sinus (white arrow), left skull base (black arrow) and right occipital bone (posterior black arrow).B Axial CT image with bone window, more cranial, shows ground-glass appearance of sphenoid bone with mild narrowing of left optic canal (arrow)
A B
Giant Aneurysm of Skull Base
Definition
Aneurysms involving the skull base.
Clinical Features
▬
Most aneurysms are acquired and spontaneous;
some occur after infection, trauma or local sur- gery. There is a small genetic predisposition.
▬
Pressure on the nerves in the cavernous sinus can lead to ophthalmoplegia or facial pain.
▬
Hemorrhage is unusual.
▬
Can rupture into the sphenoid sinus, into the sub- arachnoid space or into the cavernous sinus.
Imaging Features
▬
Large aneurysms may erode the skull base.
▬
Imaging of large aneurysms is varied and depends on the patency of the lumen and the presence of thrombosis.
▬
A dynamic scan’s arterial phase may help separate the aneurysm from the normal cavernous sinus.
▬
Calcification can be present in the aneurysm’s wall.
Figure 13.36
Giant aneurysm in skull base; 33-year-old male with his- tory of carotid aneurysm treated using balloon and coils with complete occlusion of left internal carotid artery.
A Axial CT image, bone window, shows erosion of left middle cranial fossa due to a large aneurysm (arrow).
Lumen of aneurysm is completely occluded.B Coronal CT image confirms severe bone destruction (arrow) A
B
Glomus Vagale Paraganglioma
Definition
Benign vascular tumor arising from neural crest paraganglion cells associated with nodose ganglia of vagus nerve.
Clinical Features
▬
Depending on the location of the paraganglioma, the tumor is named carotid body tumor, glomus vagale, glomus jugulare, or glomus tympanicum.
▬
Usually fourth to fifth decade; slight female domi- nance.
▬
Can occur sporadically or as autosomal dominant familial tumor.
▬
Presents with vagal neuropathy, hoarseness, Horner syndrome (glomus vagale).
Imaging Features
▬
Located in nasopharyngeal carotid space.
▬
Displace parapharyngeal fat anteriorly and inter- nal carotid artery anteromedially.
▬
Usually solitary lesions at one site.
▬
Highly vascular and intensely enhancing mass.
▬
May contain areas of hemorrhage and necrosis.
▬
T1-weighted MRI: characteristic salt and pepper appearance due to flow (pepper) and hyperinten- sity due to hemorrhage (salt).
Figure 13.37
Glomus vagale paraganglioma; 54-year-old female with symptoms of dysphagia.There was a palpable mass on the right side of the neck.A Axial T1-weighted post-Gd MRI demonstrates enhancing mass in right carotid space (arrow), consis- tent with paraganglioma.B Right common carotid angiogram demonstrates large vascular mass (arrow)
A B
Craniopharyngioma
Definition
Benign tumor derived from remnants of Rathke’s pouch.
There are two types: adamantinomatous and pap- illary.
Clinical Features
▬
Bimodal age distribution (peak 5–15 years; papil- lary type >50 years).
▬
Pediatric patient with morning headache, visual defect, short stature.
▬
Endocrine disturbances.
▬
Hydrocephalus.
Imaging Features
▬
Typically found in suprasellar location.
▬
Heterogeneous appearance with calcification and cystic component.
▬
T1-weighted MRI: signal varies with cyst contents.
▬
T1-weighted post-Gd MRI: solid portions are enhanced heterogeneously.
Figure 13.38
Craniopharyngioma; 7-year-old female with history of longstanding headache. A Sagittal T1-weighted MRI shows a large lobulated sellar/suprasellar mass extend- ing upwards to third ventricle and posteriorly into pre- pontine cistern (arrows). Most cysts show hyperinten- sity. B Axial T2-weighted MRI shows extension into cerebellopontine angles more to left (arrows) with left parasellar extension (arrowhead) and encasement of basilar artery (small arrowhead).C Axial CT shows eccen- trically located calcification within a hyperdense lobu- lated mass at suprasellar region (arrow)
A
C
B
Pituitary Macroadenoma Invading Skull Base
Definition
Pituitary macroadenoma with inferior extension to sphenoid sinus and clivus.
Clinical Features
▬
Pituitary hormonal abnormality
▬
Visual field defect and cranial nerve palsy
▬
Benign and slow-growing
Imaging Features
▬
Expansion of sella with invasion of surrounding adjacent structures.
▬
Bony margins are usually smooth.
▬
On MRI, sellar-infrasellar mass invading basisphe- noid and basiocciput.
▬
May extend into cavernous sinus and encase inter- nal carotid artery.
▬
Enhancement is necessary to evaluate the tumor extension.
Figure 13.39
Pituitary macroadenoma; 53-year-old male with visual disturbance.A Axial T2-weighted MRI shows hetero- geneous large mass in sella and right cavernous sinus (arrow). Mass extends posteriorly into brainstem caus- ing compression of brainstem.B Sagittal T1-weighted post-Gd MRI shows mass expanding sella and extend- ing up to superior portion of sphenoid sinus and clivus (arrow). Posteriorly mass extends into brainstem caus- ing compression of brainstem (arrowhead).C Coronal T1-weighted post-Gd MRI shows mass extending into right cavernous sinus (arrow) with encasement of inter- nal carotid artery (arrowhead)
A
C B
Trigeminal Schwannoma
Definition
Benign encapsulated tumor of Schwann cell arising from trigeminal nerve.
Clinical Features
▬
Trigeminal nerve is most commonly affected in central skull base.
▬
Asymptomatic mass in deep facial soft tissue.
▬
May present with facial pain, decreased sensation and masticator muscle weakness and/or atrophy.
▬
Predominantly third or fourth decade.
Imaging Features
▬
Arises in Meckel’s cave or in cistern along course of nerve.
▬
Rarely arises below skull base.
▬
Extension is common through foramen ovale and foramen rotundum, and CT imaging with bone window is best to see smooth margin of an ex- panded foramen.
▬
May have a dumbbell shape with components enlarging cavernous sinus and protruding into posterior cranial fossa.
▬
Cystic changes or necrosis typical of larger lesions.
▬
T1-weighted post-Gd fat-suppressed MRI, axial and coronal, are best to see tumor extension.
Figure 13.40
Trigeminal schwannoma; 70-year-old male with memory loss and seizures.A Axial T1-weighted post-Gd MRI shows enlarged mass (arrow) in wall of left cavernous sinus.B Coronal T1-weighted post-Gd MRI shows mass extending through foramen ovale (arrow)
A B
Metastatic Disease to Hypoglossal Canal and Clivus
Definition
Metastatic disease from extracranial primary tumor to skull base.
Clinical Features
▬
Skull base tumor can be primary or metastatic.
▬
Hematogenous metastasis from primary tumors in lung, kidney, breast, prostate, and a variety of other rare locations.
▬
Neurologic symptoms depend on location of metastatic tumor.
▬
If the hypoglossal canal is affected, symptoms may be difficulty in swallowing (dysphagia) and speech (dysarthria).
▬
Treatments for skull base tumors can be divided into medical, radiation, and surgical.
Imaging Features
▬
CT with bone window most useful to evaluate bone destruction.
▬
Sclerotic changes may be present in prostate metastasis.
▬
T1-weighted MRI is sensitive for bone metastasis.
▬
T1-weighted post-Gd MRI: fat saturation neces- sary to distinguish enhancement from normal hyperintense marrow or fat.
Figure 13.41
Metastatic disease; 55-year-old female with breast cancer presented with swallowing difficulties.A Axial T1-weighted MRI demonstrates well-circumscribed hypointense lesion involving right clivus and hypoglos- sal canal (arrow).B Sagittal T1-weighted MRI confirms well-circumscribed mass (arrow).C Axial T1-weighted post-Gd MRI demonstrates evident enhancement of tumor (arrow)
A
C B
Orbit
Orbital pathology is in many respects completely different from that seen in the maxillofacial area.
Imaging of the orbit is done after a thorough clinical examination. The clinical examination can diagnose conditions of the globe with high accuracy, but any- thing that is posterior to the globe is difficult to diag- nosis clinically, often prompting imaging of the orbit.
Both CT and MR imaging are used and in general CT imaging is the first choice for trauma and bony pathology whereas MR imaging is the superior tech- nique for soft-tissue abnormalities. Again, it is not the intention in this section of this chapter on adja- cent structures to give a full description of orbital conditions, but rather to alert the maxillofacial radi- ologist as to what may be going on in the orbit which is the closest adjacent structure to the maxillofacial area superiorly and laterally.
Orbital Infectious Disease
Definition
Orbital bacterial infection.
Clinical Features
▬
Orbital bacterial infection include retention ede- ma of the eyelid, preseptal cellulitis, preseptal abscess, orbital cellulitis, orbital abscess, subpe- riosteal abscess and cavernous sinus thrombosis.
▬
The majority are of paranasal sinus origin.
▬
May develop from infectious processes of face or pharynx, trauma, foreign bodies, or septicemia.
▬
Presents with orbital edema and painful proptosis with fever.
▬
Rapidly progressive, potentially blinding diseases.
Imaging Features
▬
Post-contrast CT imaging is first-line modality and shows inflammation and rim-enhancing hy- podense fluid collection.
▬
Post-contrast MRI is best to assess intracranial complications (meningitis, subdural empyema, cerebritis, or brain abscess).
▬
On diffusion-weighted imaging, abscess shows
hyperintensity.
Figure 13.42
Orbital abscess; 26-year-old male with periorbital pain and swelling.A Axial post-contrast CT image demon- strates soft-tissue thickening and inflammatory changes in left periorbital region with a rounded nonenhancing soft-tissue lesion in left upper eyelid (arrow) consistent with abscess. Mucosal thickening of ethmoid sinus is also present and may be the source of this abscess. B Coronal T1-weighted fat-suppressed post-Gd MRI shows diffuse enhancement within soft tis- sue of left periorbital region and nonenhanced fluid col- lection (arrow). Mucosal thickening of frontal sinus is also observed.C On diffusion-weighted imaging, abscess shows very high signal intensity (arrow) due to restricted diffusion
A
C B
Dacryocystocele, Nasolacrimal Duct
Definition
Cystic dilatation of nasolacrimal apparatus resulting from stenosis of the nasolacrimal duct.
Clinical Features
▬
Present in adults (congenital dacryocystocele is seen in infancy).
▬
History of dacryocystitis or neoplastic stenosis, prior nasoorbital/nasoethmoidal trauma or sur- gery.
▬
Intranasal mass representing inferior extension of cystocele.
Imaging Features
▬
Medial canthus cyst on CT images
▬
Enlarged osseous nasolacrimal canal
▬
Intranasal mass representing inferior extension of cystocele.
Figure 13.43
Dacrocystocele; 43-year-old female with periorbital recurrent swelling. Axial (A) and coronal (B) post-contrast CT images show left periorbital soft-tissue swelling representing orbital cellulitis. Osseous nasolacrimal canal is enlarged and rim- enhancing cystic mass is observed in medial canthus which is an infected nasolacrimal cystocele (arrows)
A B
Dermoid
Definition
Cystic lesion of orbit resulting from inclusion of ectodermal elements during closure of neural tube.
Dermoid: epithelial elements plus dermal sub- structures.
Epidermoid: epithelial elements only.
Clinical Features
▬
Most common developmental cysts involving or- bit and periorbital structures.
▬
Painless firm subcutaneous mass.
▬
Diplopia if larger.
▬
Childhood presentation more common than adult.
▬
Sudden growth or change may occur following rupture.
Imaging Features
▬
Cystic, well-demarcated, extraconal mass.
▬
Commonest location is superior temporal aspect of orbit at frontozygomatic suture, but can occur anywhere in orbit.
▬
On CT images, both epidermoid and dermoid cysts appear as a nonenhancing, low-density mass.
▬
Calcifications may be seen.
▬
May have a fat density.
▬
T1- weighted MRI: usually low signal, but may be hyperintense if fat containing
▬
T2-weighted MRI: high signal
▬
Diffusion-weighted imaging: typically high inten- sity.
Figure 13.44
Dermoid; young male with palpable lesion over nasal bridge. Axial (A) and coronal (B) non-contrast CT images show well-demarcated, thin-walled mass (arrows) in supranasal wall of right orbit
A B
Fibrous Dysplasia
Definition
Progressive replacement of normal cancellous bone by poorly organized fibro-osseous tissue.
Clinical Features
▬
Usually seen in young age group (<30 years).
▬
Orbital lesion: optic neuropathy due to optic nerve compression in optic canal.
▬
Monostotic: 70% of cases, single osseous site is affected.
▬
Polyostotic: 25% of cases, involves more than two separated sites.
▬
Usually self-limiting and often does not progress after third decade of life.
▬
McCune-Albright syndrome is a variant that con- sists of polyostotic fibrous dysplasia, skin pigmen- tation and sexual precocity.
▬
Surgical treatment for optic nerve decompression and for limited cosmetic debulking and re-con- touring of bone.
Imaging Features
▬
Affects any bone including skull, skull base and facial bones.
▬
Bone CT imaging is best for diagnosis showing expansile lesion centered in medullary space with variable attenuation.
▬
Ground-glass matrix in expansile bone lesion is typical.
▬
Abrupt or gradual transition zone between lesion and normal bone.
▬
T1- and T2-weighted MRI: usually low signal.
▬
T2-weighted MRI: occasionally high signal simu- lating a tumor.
▬
T1-weighted post-Gd MRI: variable enhancement of internal matrix.
Figure 13.45
Fibrous dysplasia; 17-year-old presents with painless prominence in left supraorbital region.A Coronal CT im- age shows dense expansile greater wing of sphenoid bone on left side. Orbital cavity is compressed (arrow).
B T1-weighted MRI shows low signal intensity from fibrous lesion in greater wing of sphenoid bone on left side consistent with fibrous dysplasia (arrow). C T1- weighted post-Gd MRI shows heterogeneous enhance- ment in expanded greater wing of sphenoid bone (arrow)
A
C
B
Langerhans Cell Histiocytosis
Definition
A benign spectrum of disorders with histiocytic pro- liferation involving the orbit.
Clinical Features
▬
Unifocal Langerhans cell histiocytosis.
▬
Presents with orbital pain, swelling and proptosis.
▬
Usually presents in first decade.
▬
Management is usually conservative, and sponta- neous healing may occur.
Imaging Features
▬
Most common orbital manifestation is a solitary osseous lesion.
▬
Orbital soft-tissue involvement without an obvi- ous bony defect is rare.
▬
On CT images, homogeneously hyperdense en- hancing mass with bony erosion or destruction.
▬
T1-weighted MRI: isointense.
▬
T2-weighted MRI: minimally to moderately hy- perintense.
▬
T1-weighted post-Gd MRI: enhancement.
▬
Differential diagnosis includes lacrimal gland tu- mors, rhabdomyosarcomas, metastatic neuroblas- toma and lymphoproliferative disease.
Figure 13.46
Langerhans cell histiocytosis of orbit; 14-year-old male with two weeks of headache, now with periorbital swelling. Clinical question of infection or mass.A Axial CT image shows homogeneous soft-tissue mass (arrow) without calcification in retroorbital and greater sphe- noid space. There is a punched-out bony lesion involv- ing sphenoid wing and posterior wall of left orbit.
B Coronal STIR MRI image demonstrates a well-defined hyperintense mass (arrow) in left lateral wall of orbit.
The mass extends into left orbit and deviates left lateral rectus muscle.C Coronal T1-weighted post-Gd MRI (arrow) shows diffuse enhancement of mass
A
C B
Neurofibromatosis
Definition
Orbital manifestations associated with neurofibro- matosis type 1 (NF-1).
Clinical Features
▬
Plexiform neurofibroma and optic nerve glioma are typical orbital manifestations in NF-1.
▬
Café-au-lait spots are earliest sign and noted dur- ing first year and tumors begin to appear in child- hood.
▬
Presents with eyelid, periorbital and facial soft-tis- sue masses, proptosis and ptosis.
▬
Malignant transformation uncommon.
Imaging Features
▬
Plexiform neurofibromas are nonencapsulated in- filtrative masses involving cranial nerve, muscle, optic nerve sheath, and sclera.
▬
T1-weighting MRI: signal intensity of plexiform neurofibromas similar to that of muscle
▬
T2-weighted MRI: often high
▬
T1-weighted post-Gd MRI: contrast enhancement usually intense.
▬
May be associated with sphenoid dysplasia, bu- phthalmos and optic canal and/or orbital fissure enlargement.
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Optic nerve glioma.
A B
Figure 13.47
Plexiform neurofibroma; 30-year-old with known neurofibromatosis presenting with periorbital swelling.
A Axial T2-weighted MRI shows a large infiltrative mass in left orbit deforming globe and extending into retro-orbital area. There are large flow voids in this highly vascular mass (arrow).B Coronal T1-weighted post-Gd MRI shows enhanc- ing mass encasing and deforming globe (arrow)
